The present invention relates to near-infrared optical sampling means and methods for providing optical communication between an optical instrument and a fluid within a bioprocessing vessel for applications including, but not limited to, pharmaceutical manufacturing, food processing, and chemical manufacturing as well as other laboratory and industrial processes.
The use of optical and electronic instrumentation to monitor and control the contents of vessels and changes taking place therein is well known in the art. Processing and storage of, for example, food, beverage, chemical, agricultural, fuel, and pharmaceutical products has historically taken place primarily in multiple-use vessels comprised of stainless steel and/or glass. Numerous hardware approaches enabling interrogation and analysis of the contents of such vessels by, for example, optical, electronic, and electrochemical techniques have been described in the art. Dissolved oxygen may be measured by, for example, electrochemical probes with oxygen-permeable membranes, as well as fluorescent sensor techniques. Measurement of pH is possible by electrochemical techniques as well as fluorescent indicators. Probes for measurement of optical characteristics of materials in rigid vessels by transmission, reflection, and attenuated total reflection (ATR) are also known in the art. Such probes are often of tubular form and primarily metal construction, protruding through a head plate or side wall of a vessel and into the material under process. Such probes are typically in direct contact with the material under process. Probes and sensors of this general description are commonly designed for robustness and longevity—tolerating use, cleaning, and often sterilization for many process cycles. Such multiple-use probes and sensors typically have form factors that are not accommodating to interfacing with single-use bioreactors, particularly flexible bioreactors and those with small working volumes. Flexible bioreactors, also known as bag bioreactors, lack rigidity—surfaces commonly distort during operation, making attachment and positioning of typical multiple-use probes difficult and unstable. Bioreactors with small working volumes simply do not have the surface area or volume to support many of the sensors and probes that are common in the art. Moreover, such prior art sensors and probes do not commonly fit within the model of single-use technology as they are not disposable and must be in contact with the process fluid, thereby requiring the cleaning, sterilization, and aseptic insertion steps that single-use technology seeks to avoid.
Regular cleaning and maintenance of multiple-use vessels is required to maintain process integrity, and sterile conditions are often necessary, demanding yet more laborious and/or costly cleaning and disinfection procedures. The maintenance, cleaning, and disinfection of multiple-use process vessels coupled with the high initial cost of the equipment has led to accelerating adoption of single-use, disposable vessels in multiple industries. These single-use vessels are most commonly constructed of polymers, and are often purchased pre-sterilized such that the user may immediately put them to use. As such single-use vessels are most commonly pre-sterilized and ready for use, sensors are commonly integrated into the vessel before sterilization and sterilized with the vessel. Any sensors or connections to the vessel that are not integrated and sterilized with the vessel may be externally sterilized and installed via aseptic ports. While use of sensors or probes that are not installed into the vessel prior to sterilization of the vessel is feasible, it is typically undesirable due to the additional labor required of the end user as well as the increased probability of contamination. Such single-use vessels offer several additional benefits over conventional multiple-use bioreactors: ease of use; reduced setup labor for end users; significantly reduced cleanup time; and lower equipment costs. Single-use disposable bioreactors are available in a variety of sizes and form factors—working volumes range from sub-milliliter to thousands of liters.
A key aspect in bioprocessing is being able to transition processes from small-scale experiments in the research lab to a large-scale production environment. The research and effort to transition from small-scale experiments to production is known as scale-up, and this process is commonly challenging and time consuming. Scale-up often comprises three major phases—the research phase where initial studies are performed and processes are selected and verified; the pilot plant phase where processes are further studied, refined, and verified in higher volume processes; and the production phase where large-scale manufacturing is performed. The conditions present in small-volume research bioreactors may be markedly different from those present in the larger bioreactors in the pilot plant and on the production floor. Indeed, processes can vary considerably even between different bioreactors in the research lab. In order to execute the scale-up process in the most efficient manner possible, it is desirable to have the ability to optimize a plurality of process parameters and constituent concentrations, and often to be able to control such parameters and constituent concentrations. Ideally such monitoring and control capabilities will be uniform throughout the various stages of scale-up. Bioreactors having working volumes of microliters to few milliliters are commonly known as micro-bioreactors, and are often configured such that multiple micro-bioreactors are used to perform experiments in parallel. Such multiplexed experiments with cell culture or fermentation processes enable evaluation of process conditions, cell lines, or other variables in an efficient manner. So-called miniature-bioreactors commonly have working volumes of tens to few hundreds of milliliters, and offer another step in the scale-up process. Similarly to micro-bioreactors, mini-bioreactors are often configured in groups for parallel experimentation, though with a working volume that better represents more standard process conditions. Due to the larger form factor, mini-bioreactors may also offer enhanced process monitoring and control functionality over micro-bioreactors. While reliable monitoring of constituent concentrations of fluids in bioprocesses such as nutrient analyte concentrations remains challenging even in large-volume bioreactors, the challenge is amplified with micro- and mini-bioreactors given the space constraints and form factors. Sensor technologies capable of providing such analyte concentration information, and ideally control of such concentrations, in bioreactors used across the product development arc from research lab to production plant are desired in the biotechnology and pharmaceutical industries.
Sensors for measurement of a variety of parameters within single-use vessels have been demonstrated. Analysis of physical and chemical conditions such as pH and dissolved oxygen (DO) is possible by means of sensors comprising fluorescent indicators. Single-use and disposable temperature and pressure sensors have been demonstrated. Optical interfaces for vessels of polymeric construction, which may be single-use and/or flexible vessels, are also known in the art, though to a far lesser extent than similar interfaces for multiple-use vessels. Interfaces for transmission, reflection, and ATR optical measurements have been disclosed, however these interfaces and ports are generally not optimized for near-infrared spectroscopic applications. Numerous polymers are available that are at least partially transparent to visible and short-wave infrared (SWIR), though these polymers are often substantially opaque or exhibit significant absorption structure at wavelengths longer than 1.5 μm.
Bioreactors commonly require frequent monitoring and strict control in order to ensure adequate environmental and nutritional conditions for fermentation, cell cultures, or similar processes contained therein. While sensors are available to measure parameters such as DO and pH as is hardware and software to control these parameters, sensors and systems to monitor nutrients and analytes in an automated fashion and control the levels thereof have historically been largely absent in the art. This is the case for both multiple- and single-use bioreactors, however sensor solutions to interface with single-use bioreactors have been particularly lacking.
Measurement of nutrients and analytes by spectroscopic methods, particularly infrared spectroscopic methods, presents a robust means to monitor said nutrients and analytes and control levels thereof within bioreactors and process vessels in general. In order to optically interface with bioprocessing vessels and their contents, integrated and robust optical interface solutions are desired. These solutions may be substantially transparent in the wavelength range of interest, and offer high measurement stability and optical throughput. The requirement of material transparency is particularly challenging for infrared spectroscopy, principally near- and mid-infrared spectroscopy, where optical absorption by many commonly used polymers is unacceptably high when polymer thicknesses are within the satisfactory range to maintain mechanical integrity.
The trend towards adoption of single-use sensors and components in bioprocesses, including single-use bioprocessing vessels, is often at odds with sensor technologies that are necessarily complex. While sensors that are entirely disposable may be preferred, such approaches may not be feasible for certain sensing methods. An alternative to disposable sensors is sensors that utilize a disposable sheath or cover that provides a barrier between a non-disposable sensor and a bioprocess. If such a sheath or cover does not substantially hinder the sensing method, non-disposable sensors with disposable covers may perform advantageously in bioprocesses using both disposable and non-disposable bioprocessing vessels.